The entire disclosure of Japanese Patent Application No. 2000-075045 filed on Mar. 17, 2000 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a sheet-like material guide apparatus of a perfecting press which prints both sides of a sheet-like material. More specifically, the invention relates to a sheet-like material guide apparatus for preventing double printing (doubling) or smudging of a sheet-like material caused when the sheet-like material touches an image on a circumferential surface of a printing cylinder before printing is performed.
2. Description of the Related Art
The above type of apparatus is disclosed, for example, in Japanese Utility Model Publication No. 1990-2595. This apparatus prints both sides of a sheet-like material at a point of contact between an upper blanket cylinder and a lower blanket cylinder. In order that the sheet-like material may not contact the upper blanket cylinder before being printed at the point of contact, the apparatus takes the following guiding measures: {circumflex over (1)} A clearance is provided between a transfer cylinder and the upper blanket cylinder. {circumflex over (2)} A vacuum is applied to the circumferential surface of the transfer cylinder to attract the sheet-like material by suction to the circumferential surface of the transfer cylinder. {circumflex over (3)} The peripheral speed of the transfer cylinder is made slightly higher than the peripheral speed of the upper blanket cylinder. {circumflex over (4)} A paper guide is provided for guiding the sheet-like material to the point of contact between the upper blanket cylinder and the lower blanket cylinder to prevent contact of the sheet-like material with the upper or lower blanket cylinder. Because of these measures, the sheet-like material, which is gripped by a gripper device of the upper blanket cylinder and guided toward the aforesaid point of contact (printing unit), is fed by the transfer cylinder while being in intimate contact with the circumferential surface of the transfer cylinder without touching the upper blanket cylinder. At this time, a trailing edge of the sheet-like material is fed at a slightly higher speed than the speed of an end of the sheet-like material gripped by the upper blanket cylinder. The fed sheet-like material travels downward and moves along the paper guide. Thus, the sheet-like material does not make contact with a site near a point of gripping change from the transfer cylinder to the upper blanket cylinder, or with the lower blanket cylinder, nor does the sheet-like material contact the upper blanket cylinder at a site close to the printing unit. Hence, trouble in printing, such as doubling or smudging, can be prevented, resulting in a marked improvement of the quality of a printing product, and a decrease in the amount of wasted paper.
The foregoing apparatus of the earlier technology has the upper and lower blanket cylinders arranged vertically in parallel. In this configuration, assume that many plate cylinders are provided in contact with the circumferential surfaces of the blanket cylinders, and an inking device is provided for each of the plate cylinders. In this case, the printing press will become so huge that problems with space and operability will occur. With such a perfecting press, therefore, a pair of blanket cylinders are generally disposed parallel in a horizontal direction, as shown in Japanese Patent No. 2,612,594 (FIG. 1). In the perfecting press shown in Japanese Patent No. 2,612,594, however, a sheet-like material contacts the circumferential surface of the blanket cylinder before being printed at a point of contact between the pair of blanket cylinders, and is thus double printed or smudged. To avoid this trouble, the aforementioned guiding measures {circumflex over (1)} to {circumflex over (4)} disclosed in Japanese Utility Model Publication No. 1990-2595 may be applied to the perfecting press. In this case, if the paper guide is disposed horizontally, the sheet-like material will move along a guide surface under its own weight. In the perfecting press, however, the guide surface lies vertically. Thus, the sheet-like material moves irregularly without moving along the paper guide, so that doubling or smudging occurs as in a case where the guiding measures are not taken.
The present invention has been accomplished in consideration of the above-described circumstances. The object of the invention is to provide a sheet-like material guide apparatus of a perfecting press having two printing cylinders arranged nearly horizontally for printing both sides of a sheet-like material, the sheet-like material guide apparatus being capable of preventing trouble in printing, such as doubling or smudging, caused by the sheet-like material touching the circumferential surface of the printing cylinder before being printed.
According to the present invention, which attains the above object, there is provided a sheet-like material guide apparatus of a perfecting press comprising a first printing cylinder and a second printing cylinder arranged nearly horizontally, the first printing cylinder having a holding device for holding a sheet-like material and being adapted to print one side of the sheet-like material, and the second printing cylinder being in contact with the first printing cylinder and being adapted to print the other side of the sheet-like material, wherein a suction guide for sucking and guiding the sheet-like material transported by the first printing cylinder is provided between a transport cylinder located immediately ahead of the first printing cylinder and the second printing cylinder, and air blowing means is provided for blowing air between the sheet-like material transferred from the transport cylinder to the first printing cylinder and a circumferential surface of the first printing cylinder.
This feature can prevent a printing trouble, such doubling or smudging, due to the sheet-like material touching the circumferential surface of the cylinder before a printing pressure is applied. Furthermore, the trailing edge of the sheet-like material does not irregularly move. Thus, the printing quality is improved, and the percentage of wasted paper is decreased.
In the sheet-like material guide apparatus, a clearance between a guide surface of the suction guide and the circumferential surface of the first printing cylinder may be progressively narrowed along a flow of the sheet-like material.
In the sheet-like material guide apparatus, transport belts running at nearly the same speed as the transport speed of the sheet-like material may be passed over the suction guide.
In the sheet-like material guide apparatus, the transport cylinder may be slightly spaced from the first printing cylinder, and the peripheral speed of the transport cylinder may be made slightly higher than the peripheral speed of the first printing cylinder, in a range in which transfer of the sheet-like material to the first printing cylinder can be performed.
In the sheet-like material guide apparatus, the suction guide may be divided into a plurality of parts in a flowing direction of the sheet-like material, and the plurality of parts may be connected to a negative pressure source.
In the sheet-like material guide apparatus, the suction guide may be composed of a suction chamber having a plurality of fans disposed in a flowing direction of the sheet-like material, and the sheet-like material may be attracted by suction to a guide surface of the suction chamber which comprises an arc-shaped porous plate.
In the sheet-like material guide apparatus, the air blowing means may have a valve, and the valve may stop blowing of air to a trailing edge of the sheet-like material held by the first printing cylinder.